Rotation angle detector

ABSTRACT

A rotation angle detector includes a magnet arranged to rotate, and a magnetic detection circuit provided with a first pair of magnetic detection elements arranged to be in combination sensitive to a first magnetic field in circumferential direction to the first surface and to a second magnetic field in normal direction to the first surface and arranged away from the rotation axis, and configured to detect magnetic flux of the magnet. A second pair of magnetic detection elements are arranged to be in combination sensitive to the first magnetic field in circumferential direction to the first surface and to the second magnetic field in normal direction to the first surface. A signal processing unit is configured to output a signal representative of a rotation angle of the magnet based on outputs of the first and second pair of magnetic detection elements.

FIELD OF THE INVENTION

The present invention is generally related to the field of rotationangle detectors, attitude control devices, automatic steering devicesand throttle devices.

BACKGROUND OF THE INVENTION

As a conventional technology, there has been proposed a rotation angledetector that reduces an influence of magnetic noise on an output signalwhen detecting a direction of a rotating magnetic field (e.g., see JP2007-10449 A).

A rotation angle detector disclosed in JP 2007-10449 A or JP 2016-514833A has a sensor disposed with a pair of magnetic detection elements in aplurality of directions with respect to a rotating magnetic field, and asignal processing part that processes a signal output from each magneticdetection element of the sensor and outputs a signal corresponding to anangle of the magnetic field. In the rotation angle detector, the signalprocessing part specifies an influence of magnetic noise by comparing aphase and an amplitude of each output of the pair of magnetic detectionelements when the magnetic field is rotated, and outputs a signal withreduced influence of magnetic noise by subtracting the influence of themagnetic noise, or by performing calculation processing such asaveraging individual outputs of the pair of magnetic detection elements.

However, although the rotation angle detector of JP 2007-10449 A or JP2016-514833 A outputs a signal with reduced influence of magnetic noise,it is necessary to arrange magnetic detection elements in a plurality ofdirections with respect to the rotating magnetic field, causing aproblem that a shape of a sensor cannot be made smaller than at least aregion where the magnetic detection elements are disposed. In addition,it is necessary to make a rotation centre of the rotating magnetic fieldsubstantially coincide with a centre of the rotation angle detector,causing a problem that an arrangement of the rotation angle detector islimited.

Hence, there is a need for a rotation angle detector wherein at leastone of these drawbacks is avoided or overcome.

SUMMARY OF THE INVENTION

It is an object of embodiments of the present invention to provide for arotation angle detector, an attitude control device, an automaticsteering device and a throttle device that are to detect a rotationangle, with a reduced size and reduced restriction on the arrangement ascompared to conventional ones.

The above objective is accomplished by the solution according to thepresent invention.

In a first aspect the invention relates to the following rotation angledetector, attitude control device, automatic steering device andthrottle device. A rotation angle detector according to the inventionincludes:

-   -   a magnet arranged to rotate; and    -   a magnetic detection IC provided with a first pair of magnetic        detection elements that have a normal line of a detection        surface in parallel with a rotation axis direction of the        magnet, are arranged in a region overlapping with the magnet,        other than on a rotation axis in a plan view in which the        rotation axis direction is a normal direction, and are        configured to detect magnetic flux of the magnet, a second pair        of magnetic detection elements arranged with a predetermined        interval from the first pair of magnetic detection elements in a        circumferential direction of rotation, and a signal processing        part configured to output a signal corresponding to a rotation        angle of the magnet based on outputs of the first pair of        magnetic detection elements and the second pair of magnetic        detection elements.

In a preferred embodiment of the rotation angle detector the signalprocessing part determines a first magnetic flux density difference inthe rotation axis direction and a second magnetic flux densitydifference in the circumferential direction of the rotation, fromoutputs of the first pair of magnetic detection elements and the secondpair of magnetic detection elements, and outputs a signal correspondingto the rotation angle of the magnet based on the first magnetic fluxdensity difference and the second magnetic flux density difference.

In the rotation angle detector the signal processing part preferablydetermines a maximum value of an amplitude of the first magnetic fluxdensity difference and a maximum value of an amplitude of the secondmagnetic flux density difference based on a rate of change in theamplitudes of the first magnetic flux density difference and the secondmagnetic flux density difference, and normalizes the amplitude of thefirst magnetic flux density difference and the amplitude of the secondmagnetic flux density difference in accordance with the maximum value ofthe amplitude of the first magnetic flux density difference and themaximum value of the amplitude of the second magnetic flux densitydifference.

The invention also relates to a rotation angle detector including:

-   -   a magnet that rotates;    -   a magnetic detection IC provided with a first two pairs of        magnetic detection elements that have a normal line of a        detection surface in parallel with a rotation axis direction of        the magnet, are arranged in a region overlapping with the        magnet, other than on a rotation axis in a plan view in which        the rotation axis direction is a normal direction, and are        configured to detect magnetic flux of the magnet, a second two        pairs of magnetic detection elements arranged with a        predetermined interval from the first two pairs of magnetic        detection elements in a circumferential direction of rotation,        and a signal processing unit configured to output a signal        corresponding to a rotation angle of the magnet based on outputs        of the first two pairs of magnetic detection elements and the        second two pairs of magnetic detection elements.

In embodiments of the rotation angle detector the signal processing unitdetermines a third magnetic flux density difference in a radialdirection of the rotation and a second magnetic flux density differencein the circumferential direction of the rotation, from outputs of thefirst two pairs of magnetic detection elements and the second two pairsof magnetic detection elements, and outputs a signal corresponding tothe rotation angle of the magnet based on the third magnetic fluxdensity difference and the second magnetic flux density difference.

In further embodiments the signal processing unit determines a maximumvalue of an amplitude of the third magnetic flux density difference anda maximum value of an amplitude of the second magnetic flux densitydifference based on a rate of change in the amplitudes of the thirdmagnetic flux density difference and the second magnetic flux densitydifference, and normalizes the amplitude of the third magnetic fluxdensity difference and the amplitude of the second magnetic flux densitydifference in accordance with the maximum value of the amplitude of thethird magnetic flux density difference and the maximum value of theamplitude of the second magnetic flux density difference.

In preferred embodiments the magnet has a magnetization direction in adirection orthogonal to the rotation axis.

In other preferred embodiments the magnet is divided into two parts by aplane passing through the rotation axis and the two parts are parallelto the rotation axis direction and magnetized in mutually oppositedirections.

Advantageously the magnet is divided into a plurality of parts by aplane passing through the rotation axis according to a rotation angle tobe detected, and the plurality of parts are parallel to the rotationaxis direction and magnetized in mutually opposite directions.

In certain embodiments the magnet is formed only at a partial anglearound a central axis.

In another aspect the invention also relates to a rotation angledetector including:

-   -   a magnet that rotates;    -   a magnetic detection IC provided with a first pair of magnetic        detection elements that have a normal line of a detection        surface in parallel with a rotation axis direction of the        magnet, are arranged in a region not overlapping with the magnet        in a plan view in which the rotation axis direction is a normal        direction, and are configured to detect magnetic flux of the        magnet, a second pair of magnetic detection elements arranged        with a predetermined interval from the first pair of magnetic        detection elements in a circumferential direction of rotation,        and a signal processing unit configured to output a signal        corresponding to a rotation angle of the magnet based on outputs        of the first pair of magnetic detection elements and the second        pair of magnetic detection elements.

In yet a further aspect the invention relates to a rotation angledetector including:

-   -   a magnet that rotates;    -   a magnetic detection IC provided with a first pair of magnetic        detection elements that have a normal line of a detection        surface in a circumferential direction with respect to a        rotation axis of the magnet, are arranged in a region not        overlapping with the magnet in a plan view in which the rotation        axis direction is a normal direction, are arranged in a region        overlapping with the magnet in a plan view in which a direction        orthogonal to the rotation axis is a normal line, and are        configured to detect magnetic flux of the magnet, a second pair        of magnetic detection elements arranged with a predetermined        interval from the first pair of magnetic detection elements in a        circumferential direction of rotation, and a signal processing        unit configured to output a signal corresponding to a rotation        angle of the magnet based on outputs of the first pair of        magnetic detection elements and the second pair of magnetic        detection elements.

The invention also relates to an attitude control device including therotation angle detector as previously described.

The invention also relates to an automatic steering device including therotation angle detector as previously described.

The invention also relates to a throttle device including the rotationangle detector as previously described.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

The above and other aspects of the invention will be apparent from andelucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, withreference to the accompanying drawings, wherein like reference numeralsrefer to like elements in the various figures.

FIG. 1 illustrates a schematic view showing a configuration example of asteering system according to a first embodiment of this invention.

FIG. 2 is an exploded perspective view showing a configuration exampleof a rotation angle detector according to the first embodiment.

FIGS. 3(a) to 3(c) are a perspective view, a plan view and a front viewexplaining a positional relationship between a Hall IC and a magnet.

FIGS. 4(a) to 4(c) shows a perspective view, a plan view and across-sectional view showing a configuration of the Hall IC.

FIG. 5 illustrates a block diagram showing a configuration of a signalprocessing part of the Hall IC.

FIG. 6 illustrates a schematic cross-sectional view to explain amagnetic-flux detection operation of the Hall IC.

FIGS. 7(a 1) to 7(a 5) and 7(b 1) to 7(b 5) are schematic diagramsshowing a relationship between a rotation angle of the magnet andmagnetic flux to be detected by the Hall IC. FIGS. 7(a 1) to 7(a 5) arefront views and FIGS. 7(b 1) to 7(b 5) are plan views.

FIGS. 8(a) and 8(b) are graphs showing outputs ΔBz and ΔBx of the HallIC, each relative to a rotation angle of the magnet.

FIG. 9 provides an exploded perspective view showing a configurationexample of a rotation angle detector according to a second embodiment.

FIGS. 10(a) and 10(b) are perspective views showing a modified exampleof a magnetization direction of the magnet.

FIGS. 11(a) and 11(b) give perspective views showing modified examplesof a shape and a magnetization direction of the magnet.

FIGS. 12(a) and 12(b) illustrate perspective views providing modifiedexamples of a shape and a magnetization direction of the magnet.

FIGS. 13(a) to 13(c) are perspective views showing modified examples ofan arrangement of the Hall IC.

FIGS. 14(a) to 14(c) illustrate perspective views showing modifiedexamples of a detection angle and a magnetization direction of themagnet.

FIGS. 15(a) to 15(c) are a perspective view, a plan view and across-sectional view showing a configuration of the Hall IC, accordingto a third embodiment.

FIGS. 16(a) and 16(b) illustrates graphs showing outputs ΔBy and ΔBx ofthe Hall IC, each relative to a rotation angle of the magnet.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particularembodiments and with reference to certain drawings but the invention isnot limited thereto but only by the claims.

Furthermore, the terms first, second and the like in the description andin the claims, are used for distinguishing between similar elements andnot necessarily for describing a sequence, either temporally, spatially,in ranking or in any other manner. It is to be understood that the termsso used are interchangeable under appropriate circumstances and that theembodiments of the invention described herein are capable of operationin other sequences than described or illustrated herein.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being restricted to the means listedthereafter; it does not exclude other elements or steps. It is thus tobe interpreted as specifying the presence of the stated features,integers, steps or components as referred to, but does not preclude thepresence or addition of one or more other features, integers, steps orcomponents, or groups thereof. Thus, the scope of the expression “adevice comprising means A and B” should not be limited to devicesconsisting only of components A and B. It means that with respect to thepresent invention, the only relevant components of the device are A andB.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment, but may. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner, as would beapparent to one of ordinary skill in the art from this disclosure, inone or more embodiments.

Similarly it should be appreciated that in the description of exemplaryembodiments of the invention, various features of the invention aresometimes grouped together in a single embodiment, figure, ordescription thereof for the purpose of streamlining the disclosure andaiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the detailed description are hereby expressly incorporatedinto this detailed description, with each claim standing on its own as aseparate embodiment of this invention.

Furthermore, while some embodiments described herein include some butnot other features included in other embodiments, combinations offeatures of different embodiments are meant to be within the scope ofthe invention, and form different embodiments, as would be understood bythose in the art. For example, in the following claims, any of theclaimed embodiments can be used in any combination.

It should be noted that the use of particular terminology whendescribing certain features or aspects of the invention should not betaken to imply that the terminology is being re-defined herein to berestricted to include any specific characteristics of the features oraspects of the invention with which that terminology is associated.

In the description provided herein, numerous specific details are setforth. However, it is understood that embodiments of the invention maybe practiced without these specific details. In other instances,well-known methods, structures and techniques have not been shown indetail in order not to obscure an understanding of this description.

FIG. 1 represents a schematic view of a configuration example of asteering system according to a first embodiment. A steering system 8 hasa rotation angle detector 1 configured to detect a steering angle of asteering shaft 20 and output a detection signal, a steering wheel 2connected to one end of the steering shaft 20, a motor 3 configured torotate a column shaft 21 via a speed reduction gear 30 for automatingsteering of the steering wheel 2, an electric control unit (ECU) 4configured to control an operation of the motor 3 in accordance with anoutput of the rotation angle detector 1, and/or to output information onthe steering angle to an electronic stability control (ESC) 7; a piniongear 5 configured to convert rotational motion of the column shaft 21into linear motion of a rack shaft 50; a wheel 6 connected to the rackshaft 50 via a tie rod (not shown) or the like; and the ESC 7 configuredto stabilize an attitude at a time of turning of a vehicle, to preventsideslip.

In the above configuration rotation of the steering wheel 2 by a drivercauses rotation of the steering shaft 20 connected to the steering wheel2. The rotation of the steering shaft 20 causes an accompanying rotationof the column shaft 21. The rotation of the column shaft 21 causes adisplacement of the rack shaft 50 via the pinion gear 5, changes anangle of a pair of wheels 6 in accordance with the displacement amountof the rack shaft 50.

The rotation angle detector 1 detects the steering angle of the steeringshaft 20 and outputs a detection signal corresponding to the detectedsteering angle. When the detection signal is input from the rotationangle detector 1, the ECU 4 calculates the steering angle of thesteering shaft 20 in accordance with the detection signal, and outputsinformation on the steering angle to the ESC 7. The ESC 7 stabilizes anattitude of a vehicle at a time of turning by controlling a brake and anengine output in accordance with the information on the input steeringangle.

Further, in automating the steering of the vehicle the ECU 4 controlsthe motor 3 in accordance with the detection signal when the detectionsignal of the rotation angle detector 1 is input. The rotation of themotor 3 is decelerated by the speed reduction gear 30, to rotate thecolumn shaft 21 to operate the steering wheel 2. It should be noted thatan output of the motor 3 may be directly transmitted to the rack shaft50 without passing through the column shaft 21.

FIG. 2 is an exploded perspective view showing a configuration exampleof a rotation angle detector 1 according to the first embodiment. FIGS.3(a) to 3(c) are a perspective view, a plan view and a front view forexplaining a positional relationship between a Hall IC 100 and a magnet110.

The rotation angle detector 1 has a magnetic detector 10 mounted withthe Hall IC 100 on a substrate 101, a columnar magnet 110 connected tothe steering shaft 20 via a gear part 12, and configured to rotate in rdirection along with rotation of the steering shaft 20 in R direction.

The magnetic detector 10 is arranged such that a mounting surface of thesubstrate 101 faces a bottom surface of the magnet 110. A point 101 c onthe substrate 101 is a point that coincides with a rotation axis of themagnet 110. The Hall IC 100 is arranged at a position offset from thepoint 101 c with its centre of magnetic detection not coinciding withthe point 101 c on the substrate 101.

The magnet 110 is magnetized parallel to the bottom surface (uppersurface) of a cylindrical column, and rotates magnetization direction Dmalong with the rotation in r direction by rotating around a central axisof the cylindrical column as a rotation axis. The rotation of the magnet110 changes the magnetic field at a magnetic detection point of the HallIC 100. A specific change in the magnetic field will be described laterin FIGS. 7(a 1) to 7(a 5) and 7(b 1) to 7(b 5).

The gear part 12 includes a gear 120 configured to rotate around a shaft120 a along with the magnet 110, a gear 121 configured to rotate aroundthe shaft 121 a, and a gear 122 configured to rotate along with thesteering shaft 20. The gear part 12 is accommodated in a case (notshown), and the shafts 120 a and 121 a are held in holes provided on aninner wall of the case. The magnetic detector 10 may be accommodated inthe case or may be disposed outside the case as long as the case is anon-magnetic body.

As an example, the Hall IC 100 is disposed at a position separated by 5mm from the bottom surface of the magnet 110, and at a positionseparated by 2 mm from the point 101 c in the radial direction.

The magnet 110 is a permanent magnet formed by using a material such asferrite, samarium cobalt, neodymium or the like. A size of the magnetis, for example, 10 mm in outer diameter and 5 mm in height.

FIGS. 4(a) to 4(c) are a perspective view, a plan view and across-sectional view showing a configuration of the Hall IC 100.

The Hall IC 100 comprises: a substrate 100 b; Hall plates 100 hl ₁ and100 hl ₂ (also collectively referred to as a Hall plate 100 hl) (a firstpair of magnetic detection elements) and Hall plates 100 hr ₁ and 100 hr₂ (also collectively referred to as a Hall plate 100 hr) (a second pairof magnetic detection elements) being provided on the substrate 100 b tohave a detection surface parallel to the surface of the substrate 100 b,and having a detection direction in a normal direction of the surface ofthe substrate 100 b, as a magnetic detection element; a magneticconcentrator 100 sl provided on the substrate 100 b to overlap on a partof each of the Hall plates 100 hl ₁ and 100 hl ₂, and configured toconvert magnetic flux in the direction orthogonal to the normaldirection into the normal direction to allow the magnetic flux to bedetected by the Hall plates 100 hl ₁ and 100 hl ₂; a magneticconcentrator 100 sr provided on the substrate 100 b to overlap on a partof each of the Hall plates 100 hr ₁ and 100 hr ₂, and configured toconvert magnetic flux in the direction orthogonal to the normaldirection into the normal direction to allow the magnetic flux to bedetected by the Hall plates Hall plates 100 hr ₁ and 100 hr ₂; and asignal processing part (100 sp, FIG. 5) configured to process signalsoutput from the Hall plates 100 hl and 100 hr, in which the Hall IC 100detects a magnetic flux density in the normal direction and thedirection orthogonal to the normal direction through signal processingdescribed next.

For example, MLX 90371 or the like made by Melexis Technologies NV isused for the Hall IC 100, a distance between the Hall plates 100 hl ₁and 100 hl ₂ is 0.2 mm, a thickness is 0.5 mm, a width in y direction is2 mm, and a width in x direction is 3 mm. For the magnetic concentrator100 sl, permalloy can be used. Further, the Hall plate 100 hl and theHall plate 100 hr are separated by 2 mm to be arranged. The widths in xdirection and y direction of the Hall IC 100 above are a size inconsideration of layout of the signal processing part or the like, andare fitted within a size of 0.2 mm in y direction and 2.4 mm in xdirection when only the Hall plate 100 hl and the Hall plate 100 hr arearranged.

FIG. 5 is a block diagram showing a configuration of a signal processingpart of the Hall IC 100. The signal processing part 100 sp of the HallIC 100 has: a multiplexer 100 mux configured to sequentially outputoutputs from the Hall plates 100 hl ₁, 100 hl ₂, 100 hr ₁, and 100 hr ₂to subsequent stages; an amplifier 100 g configured to amplify theoutput of the multiplexer 100 mux; an A/D converter 100 ad configured toconvert an analog signal output from the amplifier 100 g into a digitalsignal; a digital signal processor 100 dsp configured to process thedigital signal input from the A/D converter 100 ad; a D/A converter 100da configured to convert the digital signal output from the digitalsignal processor 100 dsp into an analog signal; and an output 100 outconfigured to output the analog signal converted by the D/A converter100 da, to the ECU 4.

The digital signal processor 100 dsp calculates the outputs from theHall plates 100 hl ₁, 100 hl ₂, 100 hr ₁, and 100 hr ₂, and storesnecessary information. The digital signal processor 100 dsp adds andsubtracts the outputs of the Hall plates 100 hl ₁ and 100 hl ₂, adds andsubtracts the outputs of the Hall plates 100 hr ₁ and 100 hr ₂, and thendetermines a rotation angle of the magnet 110 by using the calculationresults. A detailed calculation method will be described later.

FIG. 6 is a schematic cross-sectional view for explaining amagnetic-flux detection operation of the Hall IC 100. In the Hall platesof the Hall IC 100, the Hall plates 100 hl ₁ and 100 hl ₂ detect themagnetic flux density in a vertical direction of the drawing. When ahorizontal component of the drawing of magnetic flux f is B// (Bx) and avertical component of the drawing is Bz, horizontal component B// of thedrawing is induced by the magnetic concentrator 100 sl and detected asB⊥, so that the Hall plate 100 hl ₁ detects “B⊥-Bz” and the Hall plate100 hl ₂ detects “−B⊥-Bz”.

Therefore, a signal proportional to magnetic flux density 2B⊥(hereinafter referred to as “Bxl”) is obtained by taking a differencebetween the outputs of the Hall plates 100 hl ₁ and 100 hl ₂ with thesignal processing part 100 sp, and a signal proportional to magneticflux density −2Bz (hereinafter referred to as “Bzl”) is obtained bytaking a sum of the outputs of the Hall plates 100 hl ₁ and 100 hl ₂.

The operation of the Hall plates 100 hl ₁ and 100 hl ₂ described abovecan be similarly explained for the Hall plates 100 hr ₁ and 100 hr ₂. Asignal proportional to magnetic flux density 2B⊥ (hereinafter referredto as “Bxr”) is obtained by taking a difference between the outputs ofthe Hall plates 100 hr ₁ and 100 hr ₂ with the signal processing part100 sp, and a signal proportional to magnetic flux density −2Bz(hereinafter referred to as “Bzr”) is obtained by taking a sum of theoutputs of the Hall plates 100 hr ₁ and 100 hr ₂.

Since the Hall plate 100 hl and the Hall plate 100 hr are arrangedseparated by 2 mm, the Hall plate 100 hl and the Hall plate 100 hr eachdetect positionally different magnetic fields. Therefore, the differencebetween the outputs of the Hall plate 100 hl and the Hall plate 100 hris calculated as ΔBx=Bxl−Bxr (a second magnetic flux densitydifference), and ΔBz=Bzl−Bzr (a first magnetic flux density difference).ΔBx and ΔBz change along with the rotation angle of the magnet 110, andtheir correspondence will be described with reference to FIGS. 7(a 1) to7(a 5) and 7(b 1) to 7(b 5) and 8(a) and 8(b).

FIGS. 7(a 1) to 7(a 5) and 7(b 1) to 7(b 5) are schematic diagramsshowing a relationship between a rotation angle of the magnet 110 andmagnetic flux to be detected by the Hall IC 100, in which FIGS. 7(a 1)to 7(a 5) are front views and FIGS. 7(b 1) to 7(b 5) are plan views.FIGS. 8(a) and 8(b) are graphs showing outputs ΔBz and ΔBx of the HallIC 100, each relative to the rotation angle of the magnet 110.

When the rotation angle of the magnet 110 is θ=0° (FIGS. 7(a 1) and 7(b1)), magnetic fields Bzl and Bzr detected by the Hall plate 100 hl andthe Hall plate 100 hr, respectively, have same numerical values.Therefore, ΔBz equals 0. Moreover, magnetic fields Bxl and Bxr detectedby the Hall plate 100 hl and the Hall plate 100 hr, respectively, havethe same numerical values with reverse signs. Therefore, ΔBx has anegative maximum value.

Next, when the rotation angle of the magnet 110 is θ=90° (FIGS. 7(a 3)and 7(b 3)), magnetic fields Bzl and Bzr detected by the Hall plate 100hl and the Hall plate 100 hr, respectively, have same numerical valueswith reverse signs. Therefore, ΔBz has a positive maximum value.Moreover, magnetic fields Bxl and Bxr detected by the Hall plate 100 hland the Hall plate 100 hr, respectively, have same numerical values.Therefore, ΔBx=0.

Next, when the rotation angle of the magnet 110 is θ=180° (FIGS. 7(a 5)and 7(b 5)), magnetic fields Bzl and Bzr respectively detected by theHall plate 100 hl and the Hall plate 100 hr have same numerical values.Therefore, ΔBz=0. Moreover, magnetic fields Bxl and Bxr detected by theHall plate 100 hl and the Hall plate 100 hr, respectively, have samenumerical values with reverse signs (opposite to the case of θ=0°).Therefore, ΔBx has a positive maximum value.

Considering the behaviour of ΔBz and ΔBx above, transition states θ=45°(FIGS. 7(a 2) and 7(b 2)), θ=135° (FIGS. 7(a 4) and 7(b 4)) and θ=180°to 360°, a relationship between rotation angle θ of the magnet 110 andΔBz and ΔBx is such that ΔBz is proportional to sin θ and ΔBx isproportional to cos θ, as shown in FIGS. 8(a) and 8(b).

Namely, ΔBz/ΔBx=k·sin θ/cos θ=k·tan θ, so that θ=arctan (K·ΔBz/ΔBx).Note that k is a constant for normalizing a magnitude of the amplitudeof ΔBz and ΔBx and K is the reciprocal of k.

The digital signal processor 100 dsp of the signal processing part 100sp obtains outputs from the Hall plates 100 hl ₁, 100 hl ₂, 100 hr ₁ and100 hr ₂ as digital signals via the multiplexer 100 mux, the amplifier100 g and the A/D converter 100 ad, and calculates θ from the outputsobtained based on the above-described calculation method.

The θ calculated by the digital signal processor 100 dsp is convertedfrom a digital signal to an analog signal by the D/A converter 100 da,and the analog signal converted by the D/A converter 100 da is outputfrom the output 100out to the ECU 4.

Since it is necessary to determine k (or K) for calculating θ, thedigital signal processor 100 dsp has a calibration mode for determiningk (or K). When the magnet 110 is rotated 360° in the calibration mode,the digital signal processor 100 dsp records ΔBz and ΔBx. Next, thedigital signal processor 100 dsp calculates k (or K) from the respectivemaximum values ΔBzmax and ΔBxmax.

Further, as another example of the method for determining the maximumvalues ΔBzmax and ΔBxmax, the digital signal processor 100 dsp maydetermine ΔBzmax and ΔBxmax from differentiation of ΔBz and ΔBx (withrespect to θ or time), namely, from ΔBz and ΔBx of an angle or timing atwhich an inclination becomes zero.

According to the above-described embodiment, since the Hall IC 100detects the rotation of the magnet 110 by using the difference of themagnetic field in x direction and the magnetic field in z directionbetween two points, the Hall plates only need to be arranged in a singledirection with respect to the rotating magnetic field and the Hallplates do not need to be arranged in a plurality of directions, enablinga compact IC compared with a conventional one.

Further, the Hall IC 100 does not need to be arranged directly under arotation centre of the magnet 110, but the Hall IC 100 can be arrangedat a position offset from the rotation centre, achieving lessrestriction on arrangement than a conventional one. In addition, sincethe Hall IC 100 can be arranged at a position offset from the rotationcentre, the gear part 12 can be omitted by providing a cylindricalmagnet on the steering shaft 20 and arranging the Hall IC 100 withrespect to the magnet. The cylindrical magnet will be described later(FIGS. 11(a) and 11(b)).

A second embodiment is different from the first embodiment in that amagnet 110 has a semicircular cylindrical shape and the range ofrotation angles to be detected is 180°. Further, the second embodimentis applied to a throttle device such as a motorcycle or a scooter. Thesame reference numerals are given to the same configurations as those ofthe first embodiment.

FIG. 9 is an exploded perspective view showing a configuration exampleof a rotation angle detector according to the second embodiment. Athrottle device 8A is, as an example, for controlling rotation of amotor of an electric motorcycle and comprises: a throttle grip 2A to begripped by a driver of the electric motorcycle; a cylindrical sleeve200A configured to rotate while an outer wall of the cylindrical sleeve200A and an inner wall of the throttle grip 2A are fixed, and an innerwall the cylindrical sleeve 200A and an outer wall of a handlebar 21Aslide; a mount 201A provided at one end of the sleeve 200A andconfigured to fix a magnet 110A; the handlebar 21A configured to steerthe motorcycle; and a switch box 22 including a case upper part 220A anda case lower part 221A configured to accommodate a switch, a harness andthe like which are not shown, and rotatably hold the sleeve 200A. Therotation angle detector 1A according to the second embodiment has amagnetic detector mounted with a Hall IC 100A on a substrate (not shown)and a semicircular cylindrical magnet 110A that integrally rotates withthe throttle grip 2A. A configuration of the magnet 110A including amagnetization direction is shown in FIG. 11(a) or 11(b) described later.

In the above configuration, when a driver of the electric motorcyclerotates the throttle grip 2A, the sleeve 200A and the magnet 110A fixedto the mount 201A are rotated. The rotation angle detector 1A detects arotation angle of the throttle grip 2A and outputs a detection signalcorresponding to the detected rotation angle. When a detection signal isinput from the rotation angle detector 1A, the ECU or the motor controldevice, which is not shown, calculates a rotation angle and controls therotation of the motor of the electric motorcycle, in accordance with thedetection signal. It should be noted that the throttle grip 2A and thesleeve 200A rotate around the handlebar 21A by less than 180°. FIG. 9shows a state in which the driver has rotated the throttle grip 2A by90°.

According to the above-described embodiment, the same effects as thoseof the first embodiment can be applied to a throttle of an electricmotorcycle. In other words, the rotation angle detector 1A with acompact IC as compared with a conventional one can be applied to thethrottle device 8A of the electric motorcycle. Further, since thearrangement position can be offset from the rotation centre and therestriction on arrangement can be reduced as compared with aconventional one, the rotation angle detector 1A can be used even whenthe handlebar 21A occupies a space of the rotation centre.

Further, since the magnet 110A is obtained by dividing a cylindricalshape into two parts, the magnet 110A is easily installed on thehandlebar 21A as compared with a cylindrical magnet (e.g., a magnet 110b (FIG. 11(a)) or a magnet 110 c (FIG. 11(b)). The rotation angledetector 1A can be introduced without requiring a design change of thethrottle device or as an alternative component of a componentconstituting a conventional throttle device.

It should be noted that the present invention is not limited to theembodiment described above. Various modifications can be made withoutdeparting from the subject matter of the present invention. For example,the magnet 110 and the magnet 110A may be replaced with the following.

FIGS. 10(a) and 10(b) are perspective views showing a modified exampleof a magnetization direction of the magnet. The magnet 110 shown in FIG.10(a) is same as the magnet 110 of the first embodiment, and is shownfor comparison with a modified example of other magnet. The magnet 110has magnetization direction Dm in a direction orthogonal to an axis of acylindrical column in the columnar shape. A magnet 110 a shown in FIG.10(b) is obtained by dividing a columnar shape into two parts by a planepassing through the axis of a cylindrical column. Magnetizationdirections Dm of individual parts are parallel to the axial direction ofthe cylindrical column and are in mutually opposite directions. Sincethis configuration causes formation of an external magnetic fieldequivalent to that of the magnet 110 at a magnetic detection position ofthe Hall IC 100, the magnet 110 may be replaced with the magnet 110 a asit is.

FIGS. 11(a) and 11(b) are perspective views showing modified examples ofa shape and a magnetization direction of the magnet. The magnet 110 bshown in FIG. 11(a) has a cylindrical shape and has magnetizationdirection Dm in a direction orthogonal to an axis of the cylindricalshape. Since this configuration causes formation of an external magneticfield equivalent to that of the magnet 110 at a magnetic detectionposition of the Hall IC 100, the magnet 110 may be replaced with themagnet 110 b as it is. The magnet 110 c shown in FIG. 11(b) has acylindrical shape and is obtained by dividing the cylindrical shape intotwo parts by a plane passing through the axis of the cylinder.Magnetization directions Dm of individual parts are parallel to theaxial direction of the cylinder and are in mutually opposite directions.Since this configuration causes formation of an external magnetic fieldequivalent to that of the magnet 110 at a magnetic detection position ofthe Hall IC 100, the magnet 110 may be replaced with the magnet 110 c asit is.

FIGS. 12(a) and 12(b) are perspective views showing modified examples ofa shape and a magnetization direction of the magnet. A magnet 110 dshown in FIG. 12(a) is one of parts obtained by dividing a cylindricalshape by a plane passing through an axis of the cylinder and hasmagnetization direction Dm in a direction orthogonal to an axis of thecylindrical shape. Since this configuration causes formation of anexternal magnetic field equivalent to that of the magnet 110 within arange of a rotation angle of 180° where the magnet 110 d and the Hall IC100 overlap in a plan view with the axis of the cylinder as a normalline, the magnet 110 d may be replaced with the magnet 110 d when beingused within the above-described range of the rotation angle. Further,the magnet 110 d can be used as the magnet 110A of the secondembodiment. The magnet 110 d may be formed not only in a semicircle butalso at any angle. The rotation angle can be detected with a rotationangle at which the magnet 110 d and the Hall IC 100 overlap in a planview with the axis of the cylinder as a normal line. A magnet 110 eshown in FIG. 12(b) is one of the parts obtained by dividing acylindrical shape by a plane passing through an axis of the cylinder.The shape is further divided into three parts by a plane passing throughthe axis of the cylinder, in which magnetization directions Dm ofindividual parts are parallel to the axial direction of the cylinder andare in mutually opposite directions. Since this configuration causesformation of an external magnetic field equivalent to that of the magnet110 within a range of a rotation angle where the magnet 110 e and theHall IC 100 overlap in a plan view with the axis of the cylinder as anormal line, the magnet 110 e may be replaced with the magnet 110 e whenbeing used within the above-described range of the rotation angle.Further, the magnet 110 e can be used as the magnet 110A of the secondembodiment. The magnet 110 e may be formed not only in a semicircle butalso at any angle. The rotation angle can be detected with a rotationangle at which the magnet 110 e and the Hall IC 100 overlap in a planview with the axis of the cylinder as a normal line.

Although the illustrated magnets 110, 110 a to 110 e, 110 a 1 and 110 a2 are columnar or cylindrical, the shape of the magnets may be anypolygonal column shape and is not limited as long as the magnetic fluxdensity to be detected by the rotation angle detector 1 or 1A canperiodically change and the rotation angle can be uniquely determinedwith the change.

Further, the Hall IC 100 and the Hall IC 100A may be arranged asfollows.

FIGS. 13(a) to 13(c) are perspective views showing modified examples ofan arrangement of the Hall IC 100. The arrangement of the Hall IC 100with respect to the magnet 110 shown in FIG. 13(a) is same as that inthe first embodiment. It is shown for comparison with modified examplesof other arrangements of the Hall IC 100. In this arrangement the magnet110 may be the magnet 110 a (FIG. 10(b)), the magnet 110 b (FIG. 11(a)),the magnet 110 c (FIG. 11(b)), the magnet 110 d (FIG. 12(a)) or themagnet 110 e (FIG. 12(b)). The arrangement of the Hall IC 100 withrespect to the magnet 110 shown in FIG. 13(b) is same as the firstembodiment and the second embodiment in that the arrangement of the HallIC 100 is offset from the axis of the cylindrical column of the magnet110. However, it is different in that the offset amount is larger than aradius of the cylindrical column and the magnet 110 and the Hall IC 100do not overlap each other, even when the magnet 110 is rotated in a planview in which the axis of the cylindrical column is a normal line. Inthis arrangement the magnet 110 may be the magnet 110 b (FIG. 11(a)) orthe magnet 110 d (FIG. 12(a)). The arrangement of the Hall IC 100 withrespect to the magnet 110 shown in FIG. 13(c) is same as the firstembodiment and the second embodiment in that the arrangement of the HallIC 100 is offset from the axis of the cylindrical column of the magnet110. However, it is different in that the offset amount is larger than aradius of the cylindrical column, the magnet 110 and the Hall IC 100 donot overlap each other even when the magnet 110 is rotated in a planview in which the axis of the cylindrical column is a normal line, themagnetic detection direction of the Hall IC 100 is the circumferentialdirection of the magnet 110 and the arrangement in z direction isbetween an upper surface and a bottom surface of the cylindrical columnof the magnet 110. In this arrangement the magnet 110 may be the magnet110 b (FIG. 10(b)) or the magnet 110 d (FIG. 12(a)).

Moreover, the magnet 110 and the magnet 110A may be replaced with thefollowing, in accordance with a rotation angle to be detected by therotation angle detector 1 and the rotation angle detector 1A.

FIGS. 14(a) to 14(c) are perspective views showing modified examples ofa detection angle and a magnetization direction of the magnet. Themagnet 110 a shown in FIG. 14(a) is same as the magnet 110 a shown inFIG. 10(b). It is shown for comparison with modified examples of othermagnets. The magnet 110 a is obtained by dividing a columnar shape intotwo parts by a plane passing through the axis of a cylindrical column(division: ½). Magnetization directions Dm of individual parts areparallel to the axial direction of the cylindrical column and are inmutually opposite directions. As shown in the first embodiment, therotation angle that can be detected by the rotation angle detector 1 byusing this magnet 110 a is 360°. A magnet 110 a 1 shown in FIG. 14(b) isobtained by dividing a columnar shape into four parts by a plane passingthrough the axis of a cylindrical column (division: ¼). Magnetizationdirections Dm of individual parts are parallel to the axial direction ofthe cylindrical column and are in mutually opposite directions. Sincethe magnetic field formed by the magnet 110 a 1 at a magnetic detectionposition of the Hall IC 100 has a period of 180°, the rotation anglethat can be detected by the rotation angle detector 1 by using themagnet 110 a 1 is 180°. A magnet 110 a 2 shown in FIG. 14(c) is obtainedby dividing a columnar shape into eight parts by a plane passing throughthe axis of a cylindrical column (division: ⅛). Magnetization directionsDm of individual parts are parallel to the axial direction of thecylindrical column and are in mutually opposite directions. Since themagnetic field formed by the magnet 110 a 2 at a magnetic detectionposition of the Hall IC 100 has a period of 90°, the rotation angle thatcan be detected by the rotation angle detector 1 by using the magnet 110a 2 is 90°.

A relationship between the number of divisions and the detection anglesshown in FIGS. 14(a) to 14(c) described above is similarly applied tothe magnet 110 (FIG. 10(a)), the magnet 110 b (FIG. 11(a)) and themagnet 110 c FIG. 11(b)). Further, in the case of the magnet 110 d (FIG.12(a)) or the magnet 110 e (FIG. 12(b)), the detection angle is furtherhalved.

Although the magnets 110 a, 110 c, 110 e, 110 a 1 and 110 a 2 describedabove have different magnetization directions for individual parts ofthe magnet, a plurality of magnets may be prepared and arranged suchthat the magnetization directions of the adjacent magnets are differentfrom each other. The whole of the magnets may be molded with resin orthe like so as to generate the same magnetic field.

The third embodiment is different from the first embodiment in that apair of Hall plates configured to detect a magnetic flux density in ydirection is added and a rotation angle of a magnet is detected based ona difference in the magnetic flux density in y direction and adifference in the magnetic flux density in x direction. A Hall IC of thethird embodiment is applied to the rotation angle detector 1 of thefirst embodiment. Moreover, the Hall IC of the third embodiment may beapplied to the rotation angle detector 1A of the second embodiment.

FIGS. 15(a) to 15(c) are a perspective view, a plan view and across-sectional view showing a configuration of the Hall IC, accordingto the third embodiment. The Hall IC 100B comprises: a substrate 100 b;two pairs of magnetic detection elements (a first set of two pairs ofmagnetic detection elements) consisting of Hall plates 100 hl ₁ and 100hl ₂ (also collectively referred to as a Hall plate 100 hl x) and Hallplates 100 hl ₃, 100 hl ₄ (also collectively referred to as a Hall plate100 hly) and two pairs of magnetic detection elements (a second set oftwo pairs of magnetic detection elements) consisting of Hall plates 100hr ₁ and 100 hr ₂ (also collectively referred to as a Hall plate 100hrx) and Hall plates 100 hr ₃, 100 hr ₄ (also collectively referred toas a Hall plate 100 hry), being provided on the substrate 100 b to havea detection surface parallel to the surface of the substrate 100 b andhaving a detection direction in a normal direction of the surface of thesubstrate 100 b; a magnetic concentrator 100 sl provided on thesubstrate 100 b to overlap on a part of each of the Hall plates 100 hlxand 100 hly and configured to convert magnetic flux in the directionorthogonal to the normal direction into the normal direction to allowthe magnetic flux to be detected by the Hall plates Hall plates 100 hlxand 100 hly; a magnetic concentrator 100 sr provided on the substrate100 b to overlap on a part of each of the Hall plates 100 hrx and 100hry and configured to convert magnetic flux in the direction orthogonalto the normal direction into the normal direction to allow the magneticflux to be detected by the Hall plates Hall plates 100 hrx and 100 hry;and a signal processing part configured to process signals output fromthe Hall plates 100 hlx, 100 hly, 100 hrx, and 100 hry, in which theHall IC 100B detects magnetic flux densities in x and y directionsthrough signal processing described next.

A detection operation for the magnetic flux density in y direction issame as the detection operation for the magnetic flux density in xdirection described in FIG. 6 and is explained by setting By forhorizontal component B// of the drawing of magnetic flux f.

FIGS. 16(a) and 16(b) are graphs showing outputs ΔBy and ΔBx of the HallIC, each relative to the rotation angle of the magnet. Since arelationship between the rotation angle of the magnet and the magneticfield to be formed is same as that in the first embodiment, thedescription is given with reference to FIGS. 7(a 1) to 7(a 5) and 7(b 1)to 7(b 5).

When the rotation angle of the magnet 110 is θ=0° (FIGS. 7(a 1) and 7(b1)), magnetic fields Byl and Byr respectively detected by the Hall plate100 hl y and the Hall plate 100 hry have same numerical values.Therefore, ΔBy=0. Moreover, magnetic fields Bxl and Bxr respectivelydetected by the Hall plate 100 hlx and the Hall plate 100 hrx have samenumerical values with reverse signs. Therefore, ΔBx has a negativemaximum value.

Next, when the rotation angle of the magnet 110 is θ=90° (FIGS. 7(a 3)and 7(b 3)), magnetic fields Byl and Byr respectively detected by theHall plate 100 hly and the Hall plate 100 hry have same numerical valueswith reverse signs. Therefore, ΔBy has a positive maximum value.Moreover, magnetic fields Bxl and Bxr respectively detected by the Hallplate 100 hlx and the Hall plate 100 hrx have same numerical values.Therefore, ΔBx=0.

Next, when the rotation angle of the magnet 110 is θ=180° (FIGS. 7(a 5)and 7(b 5)), magnetic fields Byl and Byr respectively detected by theHall plate 100 hl and the Hall plate 100 hr have same numerical values.Therefore, ΔBy=0. Moreover, magnetic fields Bxl and Bxr respectivelydetected by the Hall plate 100 hlx and the Hall plate 100 hrx have samenumerical values with reverse signs (opposite to the case of θ=0°).Therefore, ΔBx has a positive maximum value.

Considering the behaviour of ΔBy and ΔBx above, transition states θ=45°(FIGS. 7(a 2) and 7(b 2)), θ=135° (FIGS. 7(a 4) and 7(b 4)), and θ=180°to 360°, a relationship between rotation angle θ of the magnet 110 andΔBy and ΔBx is such that ΔBy is proportional to sin θ, and ΔBx isproportional to cos θ, as shown in FIGS. 16(a) and 16(b).

Namely, ΔBy/ΔBx=k′·sin θ/cos θ=k′·tan θ, so that θ=arctan (K′·ΔBy/ΔBx).Note that k′ is a constant for normalizing a magnitude of the amplitudeof ΔBy and ΔBx, and K′ is the reciprocal of k′.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Theforegoing description details certain embodiments of the invention. Itwill be appreciated, however, that no matter how detailed the foregoingappears in text, the invention may be practiced in many ways. Theinvention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure and the appendedclaims. In the claims, the word “comprising” does not exclude otherelements or steps, and the indefinite article “a” or “an” does notexclude a plurality. A single processor or other unit may fulfil thefunctions of several items recited in the claims. The mere fact thatcertain measures are recited in mutually different dependent claims doesnot indicate that a combination of these measures cannot be used toadvantage. A computer program may be stored/distributed on a suitablemedium, such as an optical storage medium or a solid-state mediumsupplied together with or as part of other hardware, but may also bedistributed in other forms, such as via the Internet or other wired orwireless telecommunication systems. Any reference signs in the claimsshould not be construed as limiting the scope.

The invention claimed is:
 1. A rotation angle detector comprising: amagnet arranged to rotate around a rotation axis, and a magneticdetection circuit provided with a first pair of magnetic detectionelements arranged to be in combination sensitive to a first magneticfield in circumferential direction to said rotation axis and to a secondmagnetic field in normal direction to said first magnetic field andarranged away from said rotation axis, and configured to detect magneticflux of said magnet, a second pair of magnetic detection elementsarranged to be in combination sensitive to said first magnetic field incircumferential direction to said rotation axis and to said secondmagnetic field in normal direction to said first magnetic field, whereinsaid second pair of magnetic detection elements is arranged with apredetermined interval from said first pair of magnetic detectionelements in the circumferential direction to said rotation axis, and asignal processing unit configured to output a signal representative of arotation angle of said magnet based on outputs of said first and saidsecond pair of magnetic detection elements.
 2. The rotation angledetector as in claim 1, wherein said signal processing unit is arrangedto determine a first magnetic flux density difference in said normaldirection and a second magnetic flux density difference in saidcircumferential direction, from outputs of said first pair of magneticdetection elements and said second pair of magnetic detection elements,and to output a signal representative of said rotation angle of saidmagnet based on said first and said second magnetic flux densitydifference.
 3. The rotation angle detector as in claim 2, wherein saidsignal processing unit is arranged to determine a maximum value of anamplitude of said first magnetic flux density difference and a maximumvalue of an amplitude of said second magnetic flux density differencebased on a rate of change in said amplitudes of said first and saidsecond magnetic flux density difference, and arranged to normalize saidamplitudes of said first and said second magnetic flux densitydifference in accordance with the maximum values of said amplitudes ofsaid first and said second magnetic flux density difference.
 4. Therotation angle detector as in claim 1, wherein said first pair ofmagnetic detection elements is replaced by a first set of two pairs ofmagnetic detection elements and said second pair by a second set of twopairs of magnetic detection elements.
 5. The rotation angle detector asin claim 4, wherein said signal processing unit is arranged todetermine, from outputs of said first set of two pairs of magneticdetection elements and said second set of two pairs of magneticdetection elements, a third magnetic flux density difference in a radialdirection of said rotation and a second magnetic flux density differencein said circumferential direction of said rotation, and to output asignal representative of said rotation angle of said magnet, based onsaid third magnetic flux density difference and said second magneticflux density difference.
 6. The rotation angle detector as in claim 5,wherein said signal processing unit is arranged to determine a maximumvalue of an amplitude of said third magnetic flux density difference anda maximum value of an amplitude of said second magnetic flux densitydifference based on a rate of change in said amplitudes of said thirdmagnetic flux density difference and said second magnetic flux densitydifference, and arranged to normalize said amplitude of said thirdmagnetic flux density difference and said amplitude of said secondmagnetic flux density difference in accordance with said maximum valueof said amplitude of said third magnetic flux density difference andsaid maximum value of said amplitude of said second magnetic fluxdensity difference.
 7. The rotation angle detector as in claim 1,wherein said magnet has a magnetization direction in a directionorthogonal to said rotation axis.
 8. The rotation angle detector as inclaim 1, wherein said magnet is divided into two parts by a planepassing through said rotation axis and said two parts are parallel tosaid rotation axis direction and magnetized in mutually oppositedirections.
 9. The rotation angle detector as in claim 1, wherein saidmagnet is divided into a plurality of parts by a plane passing throughsaid rotation axis in accordance with a rotation angle to be detected,and said plurality of parts are parallel to said rotation axis directionand magnetized in mutually opposite directions.
 10. The rotation angledetector as in claim 1, wherein said magnet is formed only at a partialangle around a central axis.
 11. The rotation angle detector as in claim1, wherein said magnetic detection elements of said first pair arearranged in a region overlapping with said magnet.
 12. The rotationangle detector as in claim 1, wherein said magnetic detection elementsof said first pair are arranged in a region not overlapping with saidmagnet.
 13. An attitude control device comprising the rotation angledetector as in claim
 1. 14. An automatic steering device comprising arotation angle detector as in claim
 1. 15. A throttle device comprisinga rotation angle detector as in claim 1.